This invention is directed to a gate valve and more particularly to a rolling blade type of valve which is directly powered from a piston, such as an air piston.
In my patent, U.S. Pat. No. 3,916,949 issued Nov. 4, 1975, I disclose a rolling blade type of gate value for controlling the flow of dry particular material through a rectangular conduit or housing section. In that patent, the valve housing was formed with a laterally offset portion, opening into the interior of the valve, into which the rolling blade and its support arm structure moved in a retracted position. Further, the rotation or movement of the blade was by an external air cylinder working through an extension arm or lever mounted on a blade pivot pin or shaft. Thus, the torque of opening and closing the blade, applied by the air motor, was delivered through the blade through the blade mounting shaft and was not as efficient as a direct connection between the air cylinder and the blade. Further, the open offset blade-receiving housing portion at times could be a disadvantage due to the fact that material flowing through the valve conduit could also flow into the offset portion and interfere with the blade mounting and pivoting mechanisms.
In my patent, U.S. Pat. No. 3,380,475, I show an air cylinder for moving the rolling or curved blade of a gate valve in which the cylinder is connected to the blade support arm at a location close to the pivot by means of an intermediate arm extension portion. This arrangement has the advantage of operating the blade at a location outside of the flow conduit, but has the disadvantage of an awkward mechanical connection which does not take full advantage of the thrust of the air cylinder in opening the blade, due to force vectors applying force at a substantial angle to the direction of blade movement.